DESCRIPTION OF OVERALL PROGRAM (provided by applicant) This Program Project seeks to understand basic cellular mechanisms responsible for gastrointestinal (Gl) motility. Knowledge of the basic structures and mechanisms of the neuromuscular apparatus of the Gl tract provides insights about how normal Gl motility is accomplished and why dysmotilities develop in the abnormal Gl tract. The long range benefit of this information will be to provide the basis for novel methods for treatment of abnormal Gl transit and to improve the quality of life for human patients. The neuromuscular apparatus of the Gl tract is extremely complex and function depends upon integrated activity of several types of cells. We have designed 4 projects that will explore various aspects of enteric neurotransmission, pacemaker activity, and smooth muscle function. Project 1, using a novel murine genetic model in which interstitial cells of Cajal (ICC) express a fluorescent protein, will seek to understand the mechanism of pacemaker activity and how pacemaker function is affected in diabetes and ICC hyperplasia. Project 3 will seek to understand regulation of smooth muscle excitability and how the activity of non-selective cation conductances contributes to normal and abnormal responses of muscle cells. Project 4 will investigate the release, function and metabolism of a novel neurotransmitter substance that is important for regulating colonic motor function. Project 5 will study the plasticity of ICC and how and why these cells are lost in type II diabetes. This project will also seek to develop techniques for restoring networks of ICC after damage. These primary investigations will be supported by 3 Core facilities designed to provide administration and informatics support and cutting-edge techniques, including cell and organotypic cultures, construction of transgenic animals, cytometry and fluorescence activated cell sorting, analysis of molecular expression, and a variety of morphological techniques. For the purpose of translating our findings from animal models to the function of the human Gl tract, many of our experiments will be conducted on tissues and cells of human patients that have been recovered from surgery for carcinomas. The investigative team is highly synergistic and collaborative, and the PPG has a long track-record of productivity and novel discovery